Split phase fuel conditioner

ABSTRACT

A split phase fuel conditioner  10  includes a main body  20  defining an ignition chamber  22 . A transfer passage  24  is in fluid communication between the ignition chamber  22  and chamber  14 . A valve  28  selectively opens and closes a throat  26  of the transfer passage  24  to control fluid communication between chamber  22  and chamber  14 . A first injector  30  injects a first fuel volume into ignition chamber  22 . A second fuel injector  32  injects a second volume of fuel directly into transfer passage  24  through the first valve  28 . The first fuel volume is ignited in the chamber  22  to form an ignition plasma. Valve  28  is opened allowing the ignition plasma to condition the second fuel volume by vaporising the second fuel volume. The ignition plasma then sweeps the conditioned second fuel volume into the combustion chamber where it combusts in a controlled manner.

This application is a PCT national stage entry of PCT/AU02/01586 filedNov. 25, 2002, which claims Paris priority to Australian applicationPS2804, filed Jun. 7, 2002.

FIELD OF THE INVENTION

The present invention relates to a split phase fuel conditionerparticularly, though not exclusively, for diesel engines, and enginesoperating on low grade and/or low octane rated fuels.

BACKGROUND OF THE INVENTION

An inherent characteristic of large bore direct injection diesel enginesis the very short time available for the satisfactory introduction offuel into the combustion chamber. This often leads to the phenomenon ofignition delay which causes physical damage to the diesel engine as itforces peak cylinder pressure far higher than ordinarily desired. Sincethe inception of diesel engines, substantial efforts have been placed inreducing the detrimental effects of ignition delay.

Fuel technologists have attempted in part to decrease the phenomenon ofignition delay by raising the cetane value of diesel fuels. Variousengineering techniques have also been employed to reduce thisphenomenon. While some progress has been made, ignition delay stillpersists.

Ignition delay is a chemical phenomenon caused by the fact that beforeany liquid hydrocarbon fuel can spontaneously ignite from compressionheat, it must first vaporise and gather sufficient heat from the air toraise it well above its self-ignition temperature.

While in theory this may seem straight forward, it is compromised by thevery short time available during the conventional diesel cycle withinwhich to vaporise the fuel. Typically, the fuel injection period for adiesel engine is about 15 crank degrees before top dead center (TDC).Thus even for a low speed diesel engine operating at, say 1500 rpm, thistime period is less than two thousandths of a second.

The situation is further aggravated by the fact that the liquid fuelwhen it evaporates can absorb a disproportionate amount of compressionheat, and due to its much higher mass than the air, there is a reductionin the rate of heat transfer from the air to the fuel.

As a consequence, instead of the injected fuel burning as soon as it isintroduced into a main combustion chamber of the diesel engine, and thusliberate the heat value of the fuel at a controlled combustion rate, theignition delay allows the fuel to accumulate such that upon finallyreaching self-ignition temperature, all the accumulated fuel presentalong with that being injected tends to explode in an uncontrolledmanner rather than steadily burn. Consequently, very high peak cylinderpressure is created just prior to TDC which also coincides withcompression pressure reaching its maximum. When close to TDC, due to thealignment of crank bearings, fast and sympathetic expansion of thecombustion chamber is not possible. Thus, in maintaining pressure andtemperature equilibrium, a substantial proportion of the heat generatedby the fuel is simply transferred to other engine components rather thanbeing directed to useful work.

Further, the high peak pressure at TDC heavily loads the piston rings ofthe engine against its cylinder walls at a time when they aremomentarily stationary (that is, changing from the upward compressionstroke to the downward expansion stroke) and therefore unable togenerate a hydrodynamic lubrication film. This leads to unprotectedmetal-to-metal attrition further contributing to engine wear.

The present invention was developed with a view to providing a means forbetter control of the factors that govern the combustion process in adiesel engine. However embodiments of the invention may be equallyapplied to combustion engines running on low grade and/or low octanerated fuels.

SUMMARY OF THE INVENTION

According to the present invention there is provided a split phase fuelconditioner for an internal combustion engine having a main combustionchamber, said split phase fuel conditioner including:

-   a main body defining an ignition chamber;-   a transfer passage having first fluid communication means at one end    for controlled fluid communication with said ignition chamber, said    transfer passage in fluid communication with said main combustion    chamber;-   a first valve for selectively opening and closing said first fluid    communication means to control fluid communication between said    ignition chamber and said main combustion chamber,-   a first injector for injecting a first fuel volume into said    ignition chamber;-   a second injector for injecting a second fuel volume into said    transfer passage, said second fuel injector coupled to said first    valve and operable independently of said first valve; and,-   ignition means for igniting said first volume while in said ignition    chamber to form an ignition plasma;-   whereby, in use, after formation of said ignition plasma, said first    valve is opened to allow said ignition plasma to flow into said    transfer passage to mix with said second fuel/air volume of fuel    injected by said second injector, said ignition plasma conditioning    said second fuel volume by raising it to above its self-ignition    temperature to vaporise said second fuel volume and subsequently    flowing through said transfer passage into said main combustion    chamber.

Preferably said first valve includes a first valve stem; and, a valveseat disposed at an end of said transfer passage; said valve seatextending from said first fluid communication means, said first valvestem being moveable between a first position where a first end of saidfirst stem is adjacent said seat to substantially impede or shut offfluid communication between said ignition chamber and said transferpassage, said first position corresponding to said first valve being inthe closed position; and, a second position where said first end of saidfirst stem is spaced from said seat allowing substantially unimpededfluid communication between said ignition chamber and said transferpassage, said second position corresponding to first said valve being insaid opened position.

Preferably said split phase fuel conditioner includes a solenoidoperatively associated with said first valve to control movement offirst valve between said opened and closed positions.

Preferably said solenoid includes a moveable member coupled to saidfirst valve stem whereby when said solenoid is energised said moveablemember is held by magnetic force generated by said solenoid in aposition holding said valve stem in said first position.

Preferably said moveable member is an armature plate.

Preferably said first valve is arranged so that when said first solenoidis de-energised said first valve stem is moveable to said secondposition to open said first valve by fluid pressure communicated fromsaid main combustion chamber to said first valve stem through saidtransfer passage.

Preferably said solenoid includes a solenoid housing coupled to saidmain body, said armature plate being disposed within said solenoidhousing, said solenoid housing limiting motion of said armature plateand accordingly said first valve stem in a direction towards said itssecond position.

Preferably said solenoid housing contains damping means for dampingmotion of said first valve stem in said direction towards its secondposition.

Preferably said damping means includes one or more pads of resilientmaterial supported by said solenoid housing.

Preferably said damper alternately, or in addition, includes a springdisposed about an end of said first valve stem distant one end, saidspring having one end in abutment with said solenoid housing and anopposite end adapted to engage said armature plate or after said firstvalve stem travels a first distance from said first position towardssaid second position.

Preferably said split phase fuel conditioner includes a guide throughwhich said first valve stem extends, said guide sealing one end of saidignition chamber.

Preferably said guide is clamped between said solenoid housing and saidone end of said ignition chamber.

Preferably said split phase fuel conditioner includes a bellows sealattached at one end to said guide and at an opposite end about a portionof said valve stem extending beyond said guide.

Preferably said second injector includes a second valve stem extendingaxially through said first valve stem.

Preferably said second valve stern includes a head adapted to form aseal against said first end of said valve stem, said second valve stemaxially moveable relative to said first valve stem to an opened positionwhere said head is spaced from said first end of said first valve stem,whereby fuel injected through said first valve stem by said second fuelinjector can flow into said transfer passage.

Preferably said second injector includes a sleeve disposed within saidfirst valve stem and provided with an axial passage through which secondvalve stem extends, said axial passage and said second valve stemrelatively dimensioned to define the fluid flow path therebetweenthrough which said second fuel volume can flow when said second valvestem is in its opened position.

Preferably an inner circumferential surface of said sleeve is formedwith one or more helical delivery grooves to assist in imparting aspiral motion to said second fuel volume injected into said transferpassage by said second injector.

Preferably said transfer passage is formed internally of a tubeextending from said main body into said main combustion chamber througha housing of said internal combustion engine, said tube provided with alength of an outer diameter such that an air gap is formed between anouter surface of said length of said tube and said housing.

Preferably said tube is provided with one or more jet orifices throughwhich said plasma and conditioned fuel flows to enter said maincombustion chamber.

Preferably said transfer passage is of a volume approximately no morethan 2% of the clearance volume of said main combustion chamber.

Preferably said transfer is of a volume approximately no more than 1% ofsaid clearance volume.

Preferably said ignition chamber is of a volume no more than 15% of theclearance volume defined of said main combustion chamber.

Preferably said ignition chamber is of a volume between 5% to 10% ofsaid clearance volume.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way ofexample only with reference to the accompanying drawings in which:

FIG. 1 is a section view of a preferred embodiment of a split phase fuelconditioner in accordance with the present invention;

FIG. 2 is a view of section AA taken through FIG. 1;

FIG. 3 is an exploded section view of an alternate embodiment of a valveincorporated in the split phase fuel conditioner depicted in FIG. 1;and,

FIG. 4 is a view of the embodiment of the valve depicted in FIG. 3 in aclosed position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

FIGS. 1 and 2 depict an embodiment of a split phase fuel conditioner 10for an internal combustion engine 12 having a main combustion chamber 14defined between an end of a cavity in the form of a cylinder 16 and apiston 18 housed within the cylinder 16. In the present embodiment wherethe engine 12 is a reciprocating piston engine 12, the engine 12 islikely to include a plurality of combustion chambers defined betweenrespective cylinder ends and pistons. A separate split phase fuelconditioner is provided for each main combustion chamber. Forsimplicity, the following description is in relation to a single splitphase fuel conditioner 10 associated with a single main combustionchamber.

The split phase fuel conditioner 10 includes a main body 20 defining anignition chamber 22. A transfer passage 24 having first fluidcommunication means in the form of a throat 26 at one end for controlledfluid communication with the ignition chamber. The transfer passage 24is also in fluid communication with the main combustion chamber 14. Afirst valve 28 is provided for selectively opening and closing thethroat 26 to control fluid communication between the ignition chamber 22and the main combustion chamber 14.

As shown in FIG. 2, a first injector 30 is coupled with the main body 20for injecting a first fuel volume into the ignition chamber 22. A secondfuel injector 32 (shown in FIG. 1) injects a second fuel volume into thetransfer passage 24. The second injector 32 is coupled to, but operableindependently of, the first valve 28. An ignition means in the form of aspark plug 34 is also coupled to the housing 20 and extends into theignition chamber 22 to provide a spark for igniting fuel injected intothe ignition chamber 22. The ignition means may also include a glow plug36 coupled to the main body 20 and extending into the ignition chamber22 for heating the fuel/air mixture particularly at initial start-up ofthe engine 12.

In broad terms, and for the meantime not concerning ourselves withtiming issues, the conditioner 10 operates by initially injecting afirst fuel volume into the ignition chamber 22 via the injector 30 andigniting this fuel to form an ignition plasma. Thereafter the valve 28is opened to allow the ignition plasma to flow through the transferpassage 24 into the combustion chamber 14. However, prior to the valve28 opening, a second fuel volume is injected via the second injector 32into the transfer passage 24. Thus, the plasma conditions the secondfuel volume by raising its temperature above its self-ignitiontemperature vaporising the second fuel volume then sweeps theconditioned second fuel volume into the combustion chamber 14 where itseeks out oxygen within the main combustion chamber 14 and combusts in acontrolled manner, the ignition plasma acting as an ignition source forthe second fuel/air mixture. The second fuel volume may vary dependingon engine conditions and load in a convention manner.

Looking at the components of the conditioner 10 in more detail, the mainbody 20 includes an annular body 38 which is screw coupled and sealed ata lower end to a frusto-conical body 40. The main body 20 is providedwith an upper circular coolant chamber 42, a lower circular coolantchamber 44 and six vertically extending evenly spaced cooling passages46 which connect the upper coolant chamber 42 to the lower coolantchamber 44. A coolant inlet 48 leads to the upper coolant chamber 42while an outlet 50 is provided in fluid communication with the lowercoolant chamber 44. As discussed in greater detail below, the uppercoolant chamber 42 is defined between an upper end of the annular body38 and a solenoid housing 52.

The transfer passage 24 is constituted by an axial bore in a tube 54coupled to an end of the frusto-conical body 40 distant the annular body38. The tube 54 is provided with a first length 56 with a first outerdiameter and a second contiguous length 58 of a smaller outer diameter,with a stepped shoulder 59 formed therebetween. The throat 26 which isat an upper end of the passage 24 progressively widens in a upstreamdirection. An opposite end of the passage 24 branches to two separatejet orifices 60 formed in the second length 58 of the tube 54 extendinginto the main combustion chamber 14. The tube 54 extends into a cavity62 formed in a cylinder head 64 of the engine 12 which normally seats aconventional fuel injector. The shoulder 59 of the tube 54 is sealedwith a copper washer 66 to the head 64. It will also be seen that theouter diameter of the length 56 of the tube 54 is smaller than the innerdiameter of the portion of the cavity 62 through which it extends tothereby form an air gap 68 therebetween.

The portion of the cylinder head 64 which defines the cavity 62 branchesout to form a flange 70 provided with holes 72 to allow attachment ofthe split phase fuel conditioner 10 by studs (not shown) passing throughthe hole 72 and attached to the flange 70.

The volume of the passage 24 is ideally no more than 2% of the clearancevolume of the engine 12 and more preferably less than 1% of theclearance volume. The clearance volume is the volume of the combustionchamber 14 when the piston 18 is at TDC. Further, the ignition chamber22 ideally has a volume of no more than 15% of the clearance volume andmore preferably a volume of between 5% to 10% of the clearance volume.

The solenoid housing 52 includes a lower portion 74 made from amagnetisable material and provided with a plurality of cutouts forseating concentric electrical coils 76 a, 76 b and 76 c (hereinafterreferred to in general as “coils 76”). The coils 76 and lower portion 74in effect form an electromagnet. Mutually adjacent coils 76 are fed withcurrents of opposite direction to create reinforcing magnetic fields.The lower portion 74 is threadingly engaged with and sealed to an upperend of the annular body 38 of the main body 20.

The solenoid housing 52 includes an upper portion or cap 78 which isthreadingly engaged with the lower portion 74. A space 80 is formedbetween the cap 78 and the lower portion 76 through which an armatureplate 82 can vertically move. Dampers in the form of resilient pads 84are seated in the cap 78 and extend into the space 80 to dampen theupward motion of the armature plate 82. A further damper in the form ofa spring 86 is provided within the solenoid housing 52. One end of thespring 86 abuts the cap 78. An opposite end of the spring 86 is spacedfrom the armature plate 82 and, as described in greater detail below,adapted to engage the armature plate 82 and/or the valve 28 after theyhave moved through a first distance.

As is seen most clearly from FIG. 1, the coolant inlet 48 is formed inthe lower portion 74 of the solenoid housing 52. Further, the uppercoolant chamber 42 is formed between an axially depending boss 88 of thelower portion 74, an upper portion of the annular body 38 and a flangeportion 90 of a valve guide 92.

The valve guide 92 is clamped between the main body 20 and the solenoidhousing 52. More particularly, the flange 90 is seated about its lowercircumferential edge 94 in a seat 96 formed about an innercircumferential surface of the upper end of annular body 38. An upperface of the flange 90 is recessed to receive the boss 88. The uppercoolant chamber 42 is sealed by O-rings 98 and 100 disposed between theflange 90 and the boss 88, and an O-ring 102 disposed between the lowerportion 74 of the solenoid housing 52 and an upper end of the annularbody 38. A further O-ring 104 is provided between the annular body 38and frusto-conical body 40 to seal one edge of the lower coolant chamber44. An opposite edge of the lower coolant chamber 44 between the bodies38 and 40 is sealed with a copper ring 106 which also acts moresignificantly, to seal the ignition chamber 22.

The valve guide 92 includes a tubular portion 108. The flange 90 extendslaterally intermediate of the length of the tubular portion 108effectively dividing the tubular portion 108 into an upper length 110 ofconstant inner and outer diameter and a lower length 112 which has aconstant inner diameter but a reducing outer diameter in a directionaway from the flange 90. It should be appreciated that the flange 90 ofthe guide 92 effectively seals an upper end of the ignition chamber 22.

The valve 28 includes a hollow tubular valve stem 114 which is able toslide axially of the valve guide 92. A head 116 of the valve stem isprovided with a silicon nitride insert which is secured to the valvestem 114 by rolled compression swaging. The lower most end of the insert118 is tapered inwardly at 45 degrees. The insert 118 forms asubstantial seal with a valve sleeve 120 when the valve 28 is closed tosubstantially impede or shut-off fluid. The sleeve 120 is also formed ofa silicon nitride material and is disposed at an end of the transferpassage 24 adjacent the throat 26. The insert 118 and sleeve 120 arearranged so that they do not actually impact against each other when thevalve 28 is closed.

An upper end of the stem 114 extends beyond the upper length 110 of thevalve guide 92 axially through the armature plate 82 and into aconnection elbow 122 which extends through the cap 78 of the solenoidhousing 52. The connection elbow 122 includes an integrated coupled 124for coupling to a fuel hose or rail (not shown) for delivery of fuel tothe second injector 32.

The stern 114 is secured to the armature plate 82 by a shrink fit collar126 and locking nuts 128. The collar 126 is fitted about a portion ofthe stem 144 which extends beyond the upper length 110 of the guide 92but below the armature plate 82. A sealing disc 130 is disposed betweenthe collar 126 and the armature plate 82. The locking nuts 128 arescrewed onto an outer circumferential thread formed about a portion ofthe stem 114 extending beyond the armature plate 82.

An electroformed laminated nickel sealing bellows 131 forms a seal abouta portion of the stem 114 that extends beyond the upper length 110 ofthe guide 92. One end of the bellows 131 is sealed against the flange 90of the guide 92 while an opposite end is sealed against the collar 126.The bellows 131 acts as a centralising spring which, when forces orpressures are low, maintains the valve 28 opened.

The second injector 32 includes a valve stern 132 that extends axiallythrough the stem 114. Valve stern 132 is provided with a valve head 134at a lower end which, when no fluid pressure acts on the valve 32, sealsagainst the insert 118. Further, when the valve 28 is closed, the valvehead 134 also seals against an inside of the seat 120. The stem 132 isaxially slidable within a sleeve 136 which is disposed within andeffectively coupled to the stem 114. A lower portion 138 of the sleeve136 is formed with a reduced outer diameter and extends into the insert118. An upper end 140 of the sleeve 136 is flared outwardly over anupper end of the stem 114 and received within the elbow 122. A closingspring 142 is disposed about the stern 132 acting between a stop 144attached to an upper end of the stem 132 and a shoulder 146 formedinternally of the sleeve by reaming an axial passage 148 of the sleeve136 through which the valve stem 132 extends.

The passage 148 and valve stem 132 are relatively dimensioned so that agap forms therebetween creating a flow passage through which fuel canflow into the transfer passage 24 when the valve 32 is opened. Theinside surface of the sleeve 136, particularly of its lower portion 138can be provided with a spiral groove to assist in imparting spiralmotion to the fuel injected by the injector 32.

When the coils 76 are energised, the armature plate 82 is held bymagnetic force onto an upper surface of the lower portion 74 of thearmature housing 52. This places the valve stern 114, and in particularthe insert 118, in a first position where it is adjacent, and moreoverreceived in, the valve sleeve 120 to substantially impede or shut-offfluid communication between the ignition chamber 22 and the transferpassage 24. This is equivalent to the valve 28 being closed. However,when the coils 76 are de-energised, the valve stem 114 is free to slideaxially in an upward direction to a second position where the insert 118is spaced from the sleeve 120 thereby allowing substantially unimpededfluid communication between the ignition chamber 22 and the transferpassage 24. This is equivalent to the valve 28 being opened. This upwardmovement is caused by fluid pressure within the main combustion chamber14 being communicated via the passage 24 to the valve 28 via the valvehead 134 and insert 118. The resilient pads 84 and spring 86 act todampen impact of the armature plate 82 against the cap 78 when the valve28 is opened.

It is envisaged that soft closure techniques may be employed for closingthe valve 28. This involves applying a low voltage initially to thecoils 76 to gently close the valve 28 during the early phases of thecycle of the engine 10 and then at about 90° before top dead center(BTDC) applying full voltage to the coil 76 to firmly hold the valve 28in the closed position against rising compression pressure.

The operation of the split phase fuel conditioner 10 will now bedescribed in detail. Some time after completion of the previous powerstroke, and with the valve 28 closed by the application of electricalcurrent to the coils 76, the injector 30 injects a first fuel volume,mixed with air into the ignition chamber 22. Typically, the fuel/airmixture will be on the rich side. It is envisaged that the air providedto the injector 30 will be from an engine driven compressor at apressure regulated to a desired compression ratio, typically the same asthe compression ratio of the engine 12, namely about 12:1 or, leavingaside the effects of heat, about 176 psi. The air is provided to an airreceiver (not shown) from the compressor for subsequent communicationwith the injector 30.

An alternate to the use of a compressor, and practical with amulti-cylinder engine, would be the use of one of the engine's cylindersfor this compression by replacing an injector of that cylinder with asuitably designed one-way valve and pipe work to an air receiver incommunication with the injector 30. Then, at attainment of a suitablepressure surplus, pneumatically holding the engine's inlet valvepartially opened to prevent further compression. When the air receiverpressure approaches the desired ignition chamber pressure, the inletvalve of the cylinder could then be fully closed to resume compression.This reduces undue work while engine balance is maintained.

The injector 30 injects the first fuel volume mixed with or entrained inair tangential to the chamber 22 thereby resulting in a circular flow ofsaid fuel and air about the chamber 22. This fuel/air mixture is heatedby the glow plug 36 to cause vaporisation, however it is unable tospontaneously combust as there is insufficient compression heat withinthe chamber 22. Rather, ignition of the fuel/air mixture within thechamber 22 is controlled by the timing of spark plug 34. It thereforealso follows that ignition within the ignition chamber 22 is not in anyway controlled by the timing of the piston 16. Thus, injection of thefuel/air mixture via the injector 30 into the ignition chamber 22 isarranged at any suitable time to allow a sufficient period forpreparation and conditioning of the fuel/air mixture to be in idealcondition for spark ignition by the spark plug 34 just prior to TDC.

It is anticipated that the rotational turbulence caused by the injectionof the fuel/air mixture into the ignition chamber 22 will cause thefuel/air mixture to rotate several times past the glow plug 36 andassist in vaporising the fuel particularly at cold start-up.Pre-ignition within the ignition chamber 22 is voided or at least can becontrolled by maintaining the compression ratio within the chamber atabout 12:1 and reducing residence time. Further, as air is applied tothe injector 30 via an air receiver, compression heat is not availableto cause premature ignition.

Compression within the main combustion chamber 14 is achieved bymovement of the piston 18 in the conventional manner. Compressionresulting from the piston 18 results in compression of only air withinthe main combustion chamber 14. This has an advantage in terms ofemission control as fuel cannot be forced into remote areas and thusfail to combust.

At a desired moment, generally just prior to maximum compression beingreached in the main combustion chamber 14, the spark plug 34 is operatedto initiate combustion of the fuel/air mixture within the ignitionchamber 22. If the valve 28 is not opened within about 15 crank degreesthe combustion pressure within the ignition chamber 22 rises veryrapidly to near its maximum pressure. As a result of the small size andvolume of the chamber 22, and the rotational turbulence, flamepropagation within the chamber 22 is relatively fast.

It is known that for about the first five crank degrees after sparking,there is little if any measurable pressure rise. Thereafter, pressurerise is expediential. As both the valve 28 and spark plug 34 areelectronically controlled, the timing of the spark and opening of thevalve 28 can be controlled with great accuracy. An engine control unit(ECU—not shown) can be programmed with advanced curves to automaticallyadjust these functions to optimum levels with changes of engine speedand load. The ignition plasma arising from the combustion of thefuel/air mixture within the ignition chamber 22 is able to be dischargedthrough the valve 28 at a very high velocity. The velocity is by andlarge controlled by spark timing. As intimated above, it the ignitionplasma is released before 5 crank degrees after delivery of the sparkfrom the spark plug 34, its discharge velocity will be relatively low.However, if discharged at say 10 to 15 crank degrees thereafter, thepressure within the ignition chamber 22 will be substantially higherthan that in the main combustion chamber 14 and thus the velocity of theplasma discharge will be very high.

The injector 32 delivers the second fuel volume directly into thetransfer passage 24 at the conventional diesel injection time of 17-15°(BTDC) with completion before TDC, or if needed for additional heatexchange, injection of fuel through the second injector 32 can bearranged to commence slightly before the abovementioned times. Thegrooves on the inside wall of the sleeve 136 assist in imparting aspiral motion to the fuel injected via the second injector 32. Thisassists in ensuring impingement of the fuel onto the walls of the tube54 defining the passage 24. This fuel is largely vaporised by heattransfer from the tube 54. The air gap 68 enhances the transfer byinsulating to isolate the length 56 of the tube 54 from the normalcooling system of the engine 12.

Just after TDC the valve 28 is rapidly opened by shutting off current tothe coils 76 allowing the valve 28 and in particular the valve stern 114to move vertically upward against the compression pressure within themain combustion 14 being communicated via the transfer passage 24. Thus,with the insert 118 now spaced from the sleeve 120 the ignition plasmafrom the ignition chamber 22 which is at a considerably higher pressurethan the compression pressure within the main combustion chamber 14 isable to very rapidly flow through the throat 26 into the transferpassage 24 where it sweeps and collects the vaporised fuel/air mixture,with the mixture of the ignition plasma and vaporised fuel subsequentlyflowing through the jet air orifices 60 into the main combustion chamber14. As the volume of the passage 24 is very small, even at idle fuelvolumes, the mixture strength and lack of oxygen will prevent anyeffective combustion from occurring within the passage 24. However, themixture of ignition plasma and fuel vapours will burn as it leavesthrough the jet nozzles 60 in direct proportion to its ability tocombine with the abundant oxygen in the compression heated air of themain combustion chamber 14. In effect the second fuel volume injectedinto the transfer passage is raised in temperature well above the fuelsself-ignition temperature and converted into a gaseous state that hasideal characteristics to mix and combust in the oxygen rich maincombustion chamber.

The combustion process within the main combustion chamber 14 is effectedby the kinetic and thermal energy of the ignition plasma and fuel vapouremanating from the gas jets 60. This in turn is dependent on thevelocity of discharge. As previously explained, the velocity iscontrollable by the timing of the spark emanated by plug 34.Consequently, this provides a convenient method to ensure very rapid butcontrolled combustion of the main fuel volume in a consistent manner,regardless of the fuel's normal ignition qualities, and at a time whenthe main combustion chamber 14 starts to expand in a sympathetic manner.Moreover, the pressure of the ignition plasma discharge and size of jetorifices 60 can be arranged to ensure its discharge through the jetorifices 60 at sonic velocity to facilitate sonic plasma enhancedcombustion.

Such action is not practical in a conventional diesel engine due to itsdependence upon compression heat to instigate combustion which, forpractical time and heat reasons must establish combustion before TDC atthe same time the compression pressure is also approaching its maximumso compounding the resultant pressure rise. Diesel and spark ignitionengines are forced to start combustion well before TDC in order tooptimise their performance, consequently, there is no empirical dataavailable on or shortly after TDC, but consideration of such appears toafford considerable emission and operational advantages.

From the above description, it will be apparent that the total volume offuel injected during a cycle of the engine is split by the conditioner10 between the first volume injected by the injector 30 into theignition chamber 22 and a second volume injected by the injector 32directly into the transfer passage 24, thus giving rise to “split phase”combustion. It will be further apparent that the volume of fuel injectedby injector 30 into the ignition chamber 22 starts combustion before TDCin independence of the engine timing and position of piston 16. Suchindependence of timing is clearly not available with conventional dieselcycle engines.

While the above embodiment has been described largely in relation todiesel engines, the conditioner 10 is well suited for operation with lowgrade and/or low octane fuels as it allows a portion of the fuelrequired for each cycle to be conditioned and combusted prior to TDC,while also substantially vaporising the main volume of fuel which maythen be mixed with the ignition plasma which ignites the main volume offuel.

Now that an embodiment of the present invention has been described indetail it will be apparent to those skilled in the relevant arts thatnumerous modifications and variations may be made without departing fromthe basic inventive concepts. For example, while there are operationaladvantages in solenoid control of the valve 24 if desired, valve 24 maybe operated mechanically. It would be appreciated that in this eventelectronic timing still allows precision control of the fuel injector 30and spark plug 34 to facilitate ignition of a first volume of fuel/airmixture. Also, while the present embodiment is described in relation toa reciprocating piston engine it may also be applied to a rotary engine(such as the Wankel engine). In such an embodiment the main combustionchamber is defined by a cavity formed in the housing of the engine andthe rotor of the engine. The transfer tube 54 would pass through apassage in the housing. In addition, the insert 118 and sleeve 120 ofthe valve 28 may be formed with alternate configurations to thatdepicted in FIG. 1. In particular, referring to FIGS. 3 and 4, analternately configured insert 118′ and valve sleeve 120′ are depicted.In this embodiment, the insert 118′ is provided with an intermediateband 119 of reduced outer diameter and through which is formed aplurality of downwardly inclined holes 121 which extend from the outersurface of the intermediate band 119 to an axial passage 123 of theinsert 118′. The axial passage 123 has an upper length of substantiallyconstant inner diameter and a lower length of progressively increasinginner diameter so that the lower portion of the passage 123 is of ashape substantially complimentary to that of the valve head 134. Thus inthis embodiment the valve head 134 can form a substantial seal with theinside surface of the passage 123 of the insert 118′. The valve sleeve120′ in this embodiment is in the form of a short cylindrical tube ofconstant inner diameter. As the valve 28 opens and closes, the insert118′ reciprocates within the sleeve 120′ between an open position wherethe intermediate band 119 is at least partially disposed above andoutside of the sleeve 120′ allowing fluid communication between theignition chamber 22 and the transfer passage 24 via the holes 119 andpassageway 123; and a closed position where the intermediate band 119 iswholly disposed within the sleeve 120′ (as depicted in FIG. 4)substantially impeding fluid flow between the ignition chamber 22 andtransfer passage 24. The substantial impedance being provided by formingthe outer diameter of at least an upper part of the insert 118′extending from the stem 114 to be only marginally smaller than the innerdiameter of the sleeve 120′.

All such modifications and variations as would be apparent to those ofordinary skill in the relevant arts are deemed to be within the scope ofthe present invention the nature of which is to be determined from theabove description and the appended claims.

1. A split phase fuel conditioner for an internal combustion enginehaving a main combustion chamber, said split phase fuel conditionercomprising: a main body defining an ignition chamber; a transfer passagehaving a throat at one end for controlled fluid communication with saidignition chamber, said transfer passage in fluid communication with saidmain combustion chamber; a first valve for selectively opening andclosing said throat to control fluid communication between said ignitionchamber and said main combustion chamber; a first injector for injectinga first fuel volume into said ignition chamber; a second injector forinjecting a second fuel volume into said transfer passage through thefirst valve, said second fuel injector coupled to said first valve andoperable independently of said first valve, the transfer passage beingupstream of the main combustion chamber relative to a direction of flowof the second volume of fuel when injected by the second injector; andan igniter to ignite said first fuel volume while in said ignitionchamber to form an ignition plasma; wherein after formation of saidignition plasma, said first valve is opened.
 2. The conditioneraccording to claim 1, wherein said first valve comprises a first valvestem; and, a valve seat disposed at an end of said transfer passage;said valve seat extending from said throat, said first valve stem beingmoveable between a first position where a first end of said first stemis adjacent said seat to substantially impede or shut off fluidcommunication between said ignition chamber and said transfer passage,said first position corresponding to said first valve being in theclosed position; and, a second position where said first end of saidfirst stem is spaced from said seat allowing substantially unimpededfluid communication between said ignition chamber and said transferpassage, said second position corresponding to first said valve being insaid opened position.
 3. The conditioner according to claim 2, furthercomprising a guide through which said first valve stem extends, saidguide sealing one end of said ignition chamber.
 4. The conditionaccording to claim 3, further comprising a bellows seal attached at oneend to said guide and at an opposite end about a portion of said valvestem extending beyond said guide.
 5. The conditioner according to claim4 wherein said second injector includes a second valve stem extendingaxially through said first valve stem.
 6. The conditioner according toclaim 5, wherein said second valve stem includes a head adapted to forma seal against a first end of said valve stem, said second valve stemaxially moveable relative to said first valve stem to an opened positionwhere said head is spaced from said first one of said first valve stem,whereby fuel injected through said first valve stem by said second fuelinjector can flow into said transfer passage.
 7. The conditioneraccording to claim 6, wherein said second injector includes a sleevedisposed within said first valve stem and provided with an axial passagethrough which second valve stem extends, said axial passage and saidsecond valve stem relatively dimensioned to define the fluid flow paththerebetween through which said second fuel volume can flow when saidsecond valve stem is in its opened position.
 8. The conditioneraccording to claim 7, wherein an inner circumferential surface of saidsleeve is formed with one or more helical delivery grooves to assist inimparting a spiral motion to said second fuel volume injected into saidtransfer passage by said second injector.
 9. The conditioner accordingto claim 1, wherein said transfer passage is formed internally of a tubeextending from said main body into said main combustion chamber througha housing of said internal combustion engine, said tube provided with alength of an outer diameter such that an air gap is formed between anouter surface of said length of said tube and said housing.
 10. Theconditioner according to claim 9, wherein said tube is provided with oneor more jet orifices through which said plasma and conditioned fuelflows to enter said main combustion chamber.
 11. The conditioneraccording to claim 1, wherein said transfer passage is of a volumeapproximately no more than 2% of a clearance volume of said maincombustion chamber.
 12. The conditioner according to claim 11, whereinsaid transfer passage is of a volume approximately no more than 1% ofsaid clearance volume.
 13. The conditioner according to claim 1, whereinsaid ignition chamber is of a volume no more than 15% of the clearancevolume of said main combustion chamber.
 14. The conditioner according toclaim 1, wherein said ignition chamber is of a volume between 5% to 10%of said clearance volume.
 15. The conditioner according to claim 1further comprising a solenoid operatively associated with said firstvalve to control movement of first valve between said opened and closedpositions.
 16. The conditioner according to claim 15, wherein saidsolenoid includes a moveable member coupled to said first valve stemwhereby when said solenoid is energized said moveable member is held bymagnetic force generated by said solenoid in a position holding saidvalve stem in said first position.
 17. The conditioner according toclaim 16, wherein said first valve is arranged so that when saidsolenoid is de-energized said first valve stem is moveable to saidsecond position to open said first valve by fluid pressure communicatedfrom said main combustion chamber to said first valve stem through saidtransfer passage.
 18. The conditioner according to claim 17, whereinsaid solenoid includes a solenoid housing coupled to said main body,said moveable member is disposed within said solenoid housing, saidsolenoid housing limiting motion of said moveable member and accordinglysaid first valve stem in a direction towards said second position. 19.The conditioner according to claim 18, wherein said solenoid housingcontains damper for damping motion of said first valve stem in saiddirection towards its second position.
 20. The conditioner according toclaim 19, wherein said damper includes one or more pads of resilientmaterial supported by said solenoid housing.
 21. The conditioneraccording to claim 20, wherein said damper alternately, or in addition,includes a spring disposed about an end of said first valve stem distantone end, said spring having one end in abutment with said solenoidhousing and an opposite end adapted to engage said armature plate orafter said first valve stem travels a first distance from said firstposition towards said second position.
 22. A method of making a splitphase fuel conditioner for an internal combustion engine having a maincombustion chamber, comprising: providing a main body defining anignition chamber; providing a transfer passage having a throat at oneend for controlled fluid communication with said ignition chamber, saidtransfer passage in fluid communication with said main combustionchamber; providing a first valve for selectively opening and closingsaid throat to control fluid communication between said ignition chamberand said main combustion chamber; providing a first injector forinjecting a first fuel volume into said ignition chamber; providing asecond injector for injecting a second fuel volume into said transferpassage through the first valve said second fuel injector coupled tosaid first valve and operable independently of said first valve, thetransfer passage being upstream of the main combustion chamber relativeto a direction of flow of the second volume of fuel when injected by thesecond injector; and, providing an igniter to ignite said first fuelvolume while in said ignition chamber to form an ignition plasma;wherein after formation of said ignition plasma, said first valve isopened.
 23. A method of using a split phase fuel conditioner for aninternal combustion engine having a main combustion chamber, the methodcomprising: providing a main body defining an ignition chamber;providing a transfer passage having first fluid communication means atone end for controlled fluid communication with said ignition chamber,said transfer passage in fluid communication with said main combustionchamber; providing a first valve for selectively opening and closingsaid first fluid communication means to control fluid communicationbetween said ignition chamber and said main combustion chamber;providing a first injector for injecting a first fuel volume into saidignition chamber; providing a second injector for injecting a secondfuel volume into said transfer passage through the first valve, saidsecond fuel injector coupled to said first valve and operableindependently of said first valve, the transfer passage being upstreamof the main combustion chamber relative to a direction of flow of thesecond volume of fuel when injected by the second injector, providing anigniter to ignite said first fuel volume while in said ignition chamberto form an ignition plasma; and after forming said ignition plasma,opening said first valve.